The present invention relates to a time-division multiplexed switching network in a time-division broadband exchanger.
In a time-division broadband exchanger using signals having frequencies of several hundred of MHz or higher, signal delays in the wiring pose a problem. In order to solve this problem, it is known to use a frame synchronization technique. An arrangement of the conventional time-division broadband exchanger is described in U.S. patent application Ser. No. 101,759 filed on Sept. 28, 1987.
In the conventional time-division broadband exchanger, in order to solve the problem of signal delays in the wiring, a frame synchronization signal generator adds a frame synchronization signal to data signals on an input bus. The exchanger is constituted by a plurality of input buses, a plurality of output buses, a space switch arranged between the input buses and the output buses for performing signal exchange between the input and output buses frame synchronization signal generators for providing the corresponding input buses with frame synchronization signals, respectively, a plurality of multiplexers connected in series with each of the input buses for multiplexing the data signals and the frame synchronization signal, respectively, a plurality of demultiplexers connected in series with each of the output buses for demultiplexing signals on the output buses, respectively, a control memory for controlling the space switch, and a plurality of phase difference detectors arranged at the input terminal of the space switch. The phase difference detector controls an output frame phase of the frame synchronization signal generator so that the frame phase of each input bus is aligned with the reference phase of the space switch. In this manner, the entire switching network can be synchronously operated while compensating for signal delays.
However, since this exchanger is constituted by the multiplexers, demultiplexers and the space switch, exchange of the data signals multiplexed on the buses on the time base cannot be performed. Therefore, when multiple stages of exchangers are to be connected, the probability of blocking of the space switches is increased. This makes it difficult to constitute a large-capacity exchanger.